350 MAG MPI over heating

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Answers

  • Handymans342Handymans342 Posts: 10,375 ✭✭✭✭✭
    I agree with Ras
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  • raybo3raybo3 Posts: 5,614 admin
    How old are the manifolds and raisers???????
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • Handymans342Handymans342 Posts: 10,375 ✭✭✭✭✭
    My boat was running warm because it was sucking air from the strainer top
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  • Dream_InnDream_Inn Posts: 7,937 mod
    One thing for sure, if it is drawing in air, it can significantly affect the amount of water it's pulling because it may lose prime.  It only takes a small leak for that to happen.  It's the same reason when you have wear in the plate on the inside of the pump. That small wear can cause that loss of prime.  It happened to me when I replaced my impeller this year.  The old impeller was worn enough to match the grooves on the plate, still allowing suction.  The new one lost prime, thus I had to buy a new pump.

    Dream 'Inn III -- 2008 400 Express

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  • rasburyrasbury Posts: 8,956 ✭✭✭✭✭
    oh I sure went through that Dream......I know that story well! It takes very little to lose that pressure......
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  • Black_DiamondBlack_Diamond Posts: 5,439 ✭✭✭✭✭
    Yes, it was the blue plug on the water pump itself. 

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • Handymans342Handymans342 Posts: 10,375 ✭✭✭✭✭
    Gee BD, my wife could have figured that one out
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  • rasburyrasbury Posts: 8,956 ✭✭✭✭✭
    easy Handy.......I'm going to check my plugs!
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  • PartsManPartsMan Posts: 246 ✭✭✭
    how many plugs on the merc 350?
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  • Dream_InnDream_Inn Posts: 7,937 mod
    PM, it depends on if you're closed cooling or not.  You will have two on the seawater pump, one on thermostat, then if you have the one drain system, one on the bottom of it.  But, if it doesn't then you'd have a couple on the engine block.

    Dream 'Inn III -- 2008 400 Express

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  • PartsManPartsMan Posts: 246 ✭✭✭
    I have closed cooling. I thought there were 5 but I only could find 4 
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  • pmerklingerpmerklinger Posts: 12 ✭✭
    Noticed on my 320 (bravo 3) that the starboard temp would rise slightly when under load,not enough to set off the alarm. When I pulled the boat out for storage I noticed that the lower end water intake has the bottom three holes plugged with zebra muscles . Might be something to looked at. Good ole Lake Erie.  Pedro

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  • Michael TMichael T Posts: 7,241 ✭✭✭✭✭

    @pmerklinger, that's interesting. I'm having my boat hauled-out for the winter this week. I'll be sure to look at the drive intakes while we are removing them to check the drive alignments.

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  • Black_DiamondBlack_Diamond Posts: 5,439 ✭✭✭✭✭
    Well, took the boat out for a run before haulout this morning, same problem.  Overheats in probably less than a minute under load, cools right off at idle.  Obviously not the raw water pump nor the winterizing drain plug.

    I'll pull the thermostat out and check it in a pot of hot water, but I don't think that's  the problem.

    I'll pull the exhaust at look at the flapper valve and go from there...

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • Michael TMichael T Posts: 7,241 ✭✭✭✭✭
    edited October 2015
    My money is on a restriction in water hoses either before or after the thermostat. Before thermostat spongy hose that collapses or restriction, after the thermostat obstruction in hose, like a burned flapper. Fingers crossed for an inexpensive fix.
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  • raybo3raybo3 Posts: 5,614 admin
    How old are the risers and manifolds???????? 
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • Black_DiamondBlack_Diamond Posts: 5,439 ✭✭✭✭✭
    Risers and manifolds are original (2003).  All fresh water usage though.

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • raybo3raybo3 Posts: 5,614 admin
    Yeah BD but still 12 years old. Maybe you should atleast check them...
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • Black_DiamondBlack_Diamond Posts: 5,439 ✭✭✭✭✭
    I'll pull them and check the shutters too. Only so many things it can be!

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • raybo3raybo3 Posts: 5,614 admin
    Good luck bro....
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • Dream_InnDream_Inn Posts: 7,937 mod
    BD, 12 years is a long time no matter if it's fresh water or not.  If the risers have never been pulled off and checked, then it is definitely a possibility that is the issue.  Good luck and let us know what you find.  BTW, you hadn't made it back down to my area this year for a ride on the Chesapeake!

    Dream 'Inn III -- 2008 400 Express

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  • SanityCheckSanityCheck Posts: 25 ✭✭
    Google "bravoitis"

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  • rasburyrasbury Posts: 8,956 ✭✭✭✭✭
    I'd start with that thermostat, we always jump to the worst scenario and often the most simple- been laud up all winter- runs fine at idle but maybe not moving enough water at higher rpm?
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  • Black_DiamondBlack_Diamond Posts: 5,439 ✭✭✭✭✭
    The HotRod 9.9 is awesome!  My AB rib flies through the water. Fun!!

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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